What is it really like to be autistic? Thomas Clements, from Great Sampford, knows.

He has Asperger’s syndrome and is bright enough to write books about it. He is fluent in several languages, and he has lived in Germany and China.

But people with autism are as different as people without it. His brother Jack, 26, is in another part of the spectrum and needs daily care for the most basic functions.

Now Thomas, 29, from Great Sampford, has written a book, The Austic Brothers, about their lives and the struggles of parents. He wants to dispel the common myths about autism.

It is not true, he says, that people with autism cannot empathise with other people. Even Jack, who barely speaks, except to endlessly repeat phrases from the films he loves - over and over and over again - instantly senses if his mother is upset.

Jack’s first spontaneously constructed sentence was: “Are you okay, mum” after their pet cat had scratched her so viciously that blood poured out of her.

Thomas, as a child, was devastated by television coverage of the famine in Ethiopia. “I could not understand why those around me weren’t reacting hysterically at the sight of skeletal children, too frail to stand or speak,” he recalled.

Aged seven, when his great aunt, Colleen, took him to see shows in London, he made her give money to each homeless person they passed because he thought they might also starve to death.

Having been bullied at school, Thomas also has a sharp insight into the psyche of the bully.

“He wound me up each time a teacher called my name in the register...I reacted with characteristic Aspergian earnestness: ‘Why do you feel the need to keep saying this?’ I eventually realised why he did it. He craved attention, because he himself was a wretched, insecure individual. His parents were divorced which clearly troubled him and he was, quite frankly, stupid. He was barely able to write a complete sentence without help from the classroom assistant. At the time, I just thought he was evil. I had no appreciation of the fact he was projecting his own inadequacies on me.”

He adds: “Jack is too innocent to be bullied. A person would have to have a heart of stone to target him.”

Thomas writes: “It’s quite funny that I’m labelled the high functioning one. I can perform daily tasks. I can converse, I can go to restaurants on my own, I can cook and I can travel independently. Jack can’t do any of these but Jack doesn’t suffer for it.

“There isn’t a any hint of worry or neurosis etched into his face whereas mine has been ravaged by fear, uncertainty and periods of extreme nihilism, mainly due to having to navigate my way through the perils of social interaction and then failing on a very consistent basis.”

When the two of them were bought roller blades, Thomas was scared to tears and Jack was off like a rocket, nearly ending up in a lake.

Another myth, says Thomas, is that of the autistic savant - fewer than eight per cent of people with autism have outstanding mathematical talents. Jack will need full-time care for the rest of his life, including help to keep his bottom clean.

Thomas said: “The idea that autism is a strength neglects the reality that a large number are so disabled both physically and mentally as to be actually quite tragic. When I see left-wing posturing online about autism being an identity as opposed to a disability, I seethe. The radical activists rarely know what autism is like for the parents of profoundly disabled kids.”

There are no cures with therapies or diets, even if well-intentioned friends ask: “Is Jack’s autism better now?”

But Jack is a happy lad. Thomas pays tribute to St Elizabeth’s College in Much Hadham, Hertfordshire, where the activities include horse riding, gardening and social enterprises, where Jack works in a shop, raising funds for the college and earning a pay packet.

“It’s astonishing how they have transformed his life and those of his parents. The staff there live and breathe compassion.”

But despite Thomas’s talent for languages and for writing, he says: “The world of human relationships, interpersonal communication and socialising is far too abstract, chaotic and even nightmarish for the relentlessly logical autistic brain to figure out. This is where Jack and I are indeed similar.

“A chat with me is usually dominated by what I wish to talk about. I am practically blind to facial expressions. I cannot read boredom in a person’s face, nor anger, nor embarrassment. The concept of body language is one that I can’t easily grasp.”

Autistic people have huge ability to focus. (Sir Isaac Newton, would just think for two hours - which irritated his widowed mother who was trying to run a working farm.)

Says Thomas: “I guess the neuro-typical mind will always consider such behaviour strange and alien but it’s okay because the daily need for inane, superficial chatter is equally puzzling to our minds.”